For various reasons some persons lose control of the sphincter muscle that opens and closes the urethra leading from the bladder whereby urinary incontinence results. In the past various devices has been proposed for implantation in the human body for remedying this condition. Such devices are shown for example in U.S. Pat. Nos. 3,744,063, 3,863,622, 3,854,469, 3,903,894, and 4,019,499. They include a resilient inflatable cuff or other member that surrounds the urethra and which when inflated squeezes the urethra closed and when deflated permits it to be open. In some cases such prior devices have included valves for controlling the flow of fluids to and from the inflatable member and consequently may be subject to malfunction in the event a valve fails to open or close properly. In other cases the prior devices contain the actuating liquid in a bulb of flexible material that is subject to unlimited manually applied pressure that may cause excessive pressure on the actuating liquid with damage to or rupture of the parts.